Question

Which region is NOT part of the extrapyramidal system?

A

orbitofrontal cortex

B

caudate

C

globus pallidus

D

cerebellum

Answer 1

The correct answer is (a)orbitofrontal cortex

This is because orbitofrontal cortex forms a part of the pyramidal system and is not a part of the extrapyramidal system.

What is pyramidal system and extrapyramidal system?

Well, these two are systems that include the motor neurons that have descending pathways.

These descending pathways are divided into two categories depending upon their functionality.

Extrapyramidal system of tracts have many synapses in their descending path with structures such as cells of nuclei of the striatum(caudate and putamen- present in basal ganglia), globus pallidus, hypothalamus and nuclei of the reticular formation. They are involved with coordination of large muscle groups used in maintenance of upright posture, in locomotion, and in head and body movements.

• main structure : corpus striatum
• rely centres: substantia niagra, subthalamic nuclei thalamus, red nucleus,reticular formation and cerebellum.
• tracts: rubrospinal, tectospinal, reticulospinal , vestibulospinal.

Pyramidal system have neurons whose axons pass without any relay. They originate from the motor cortex,area 4, area 6, somatosensory areas 1 and 2. They have their functions over motor neurons that control muscles involved in fine movements.

• tracts: lateral corticospinal, ventral corticospinal, corticobulbar.